I caught a show on Nova called The Elegant Universe a few years ago that shows where previous General Relativity and Quantum Theory are being attempted to be explained within a unified "String theory". Basically, as I understand it, Newton and Einstein (and others) only accounted for a fraction of physics that they could observer/were aware of. Newton had no idea about quantum mechanics because it wasn't a reality in his day. After Einstein came out with general relativity, he realized general relativity only governed large objects and realized his equations fell flat on the quantum level and died trying to account for his "theory of everything".

Today, String theory is trying to come up with equations which attempt to approximate Einsteins general relativity equations when describing large objects, Newtons gravity and quantum theory (as well as more odds and ends) for small objects into a single theory for all of physics.

I suggest looking for a better visual aid than The Elegant Universe if you're like me and prefer flashy pictures instead of reading books. The show itself and the guy who hosts it, Brian Greene, are a little heavy on the dramatics but are light on the more interesting details.

Although several String theories exist, to indicate the physicists still have their work cut out for them, but they seem to settle on a possibility for ten dimensions. I had a hard time imagining ten dimensions before, but a luck of turn would happen and I found an author who wrote a book amazingly titled, The Tenth Dimension and a piece of animation on the books' website which instructs in plain examples how to imagine all ten dimensions. Given my previous aversion to reading books, I was left with watching the animation and after numerous views I could follow the display all the way through.

"The three principal virtues of a programmer are Laziness, Impatience, and Hubris. See the Camel Book for why." -- `man perl`